The present invention relates to an improved brush block and, more particularly, to a brush block assembly having a latching terminal subassembly and a cartridge subassembly which may be snapped into the end cap of an electric motor.
The electric motor in which the present invention is utilized may include a low-cost alternating current (AC) universal motor or a synchro in which the slip rings are replaced by brushes. However, the motor most often associated with the present invention is a direct current (DC) motor known as a cube motor. The cube motor is typically one inch high, one inch deep and one inch thick. It is used in applications where a small prime mover is required, such as a typewriter or a portable tape recorder. To meet the limitations of space within a prior art motor, the brushes associated with the commutator have been constructed from spring material, such as beryllium copper, to which the commutator engaging brush block material was soldered. The spring material was then soldered to a terminal which passed through the housing of the motor where electrical connection was completed.
This prior art configuration required the assembly of the motor and brush block assembly before such mechanical features as end play, total indicator run out of the shaft and rotational friction could be checked. If the mechanical features were not within acceptable tolerances, the motor would have to be disassembled and corrected. This increased requirement of time during assembly and checkout, added to the motor cost.
The utilization of a threaded cartridge which houses a spring and brush block is also well known in the art. See, for example, U.S. Pat. No. 3,418,505. However, in small motors, such as a cube motor, the threaded cartridge is not an acceptable design. Other known mechanical means for connecting a brush block assembly securely into the end cap of a motor are also unacceptable in a small motor, due to size restrictions.